AbstractM dwarfs are the most numerous and long-lived stars and therefore can provide valuable information about the Galaxy and star/planet formation. However, their basic properties are tricky to measure using standard techniques for solar stars; they are intrinsically faint at visible wavelengths and their optical spectra exhibit strong molecular absorption.

I will present the metallicity and effective temperature techniques developed for M dwarf stars based on absorption features present in their modest resolution (R ~2700) K-band spectra and other ones based on their colors. These techniques have been calibrated using FGK+M dwarf pairs and synthetic atmosphere models. I will compare their results with other empirical measurements of low mass stars in the literature, and I will discuss the usefulness of the K-band methods for the characterization of exoplanet systems. Finally, I will show a new photometric technique based on IR/Optical magnitudes that provides [Fe/H] estimates accurate to RMSE ~0.12 dex for thousands of early M dwarfs in the SUPERBLINK survey.